Fiber reinforced composite materials composed of reinforcement fiber and matrix resin have been in wide use in such areas as aerospace industry, sporting goods manufacturing, and other general industries since they can be designed in a variety of forms by taking advantage of good features of reinforcement fiber and matrix resin.
The fibers that can be used as reinforcement include glass fiber, aramid fiber, carbon fiber, and boron fiber. Both thermosetting resins and thermoplastic resins may serve as matrix resin, but thermosetting resins are in wide use because they serve easily to impregnate reinforcement fiber. Useful thermosetting resins include epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, bismaleimide resin, and cyanate resin, which are combined with a curing agent or curing catalyst to provide a resin composition.
Various methods are available for the production of fiber reinforced composite materials, but attention is now focused on RTM (resin transfer molding), a low cost production method that uses a mold containing reinforcement fiber base material to which liquid thermosetting resin is added and cured by heating to produce fiber reinforced composite material.
In many processes of producing fiber reinforced composite material by the RTM method, reinforcement fiber base material is first processed into preform in a similar shape to the intended product and then the preform is placed in a mold followed by adding liquid thermosetting resin.
There are some known preform preparation methods including the production of three dimensional blades from reinforcement fiber and the stacking and stitching of sheets of woven fabric of reinforcement fiber. A known method with high general versatility is the use of a hot melt binder (tackifier) to stack and shape sheets of base material such as woven fabric of reinforcement fiber.
As a binder component, Japanese Unexamined Patent Publication (Kokai) No. 2005-194456 has disclosed a resin composition that can make strong contact with reinforcement fiber composed of thermoplastic resin and epoxy resin. When preparing preform by using this resin composition as a binder, it is necessary to heat the preform mold to melt the binder so that woven fabric base sheets come in strong contact with each other and cool the preform mold to solidify the binder. In this way, heating and cooling of the preform mold is a time-consuming step and accordingly, the preform preparation period cannot be shortened largely as long as the resin composition according to Japanese Unexamined Patent Publication (Kokai) No. 2005-194456 is used as a binder.
Compared to this, Published Japanese Translation of PCT International Publication JP HEI 8-509921 has disclosed a resin composition to serve as a binder. Specifically, a resin composition with curing reactivity which consists of an epoxy resin such as liquid bisphenol A type epoxy resin and a catalyst such as ethyl triphenyl phosphonium acetate is used as a binder and the binder is partially cured by heating to produce preform with high peel strength. Even in that case, however, heating and cooling of the preform mold is still necessary, failing to shorten the preform preparation period. Furthermore, Published Japanese Translation of PCT International Publication JP 2001-524171 discloses a binder resin composition in the form of a thermosetting mixture that consists of thermosetting resin and thermoplastic resin. However, although fiber reinforced composite materials produced by molding have largely improved interlayer toughness, heating and cooling of the preform mold is still necessary and it cannot serve to shorten the preform preparation period.
It could therefore be helpful to provide a binder resin composition that can fix bases quickly without heating and cooling a preform mold and also provide a reinforcement fiber base, preform, and fiber reinforced composite material produced therefrom.